Formula Four is the urethane that put Spitfire where it is: it doesn't flatspot when braking and maintains speed on rough terrain, where other wheels die.
This is the 97A version, one of the softer wheels in the street range. It absorbs bad asphalt and sidewalk joints while still sliding when needed. With a 58mm diameter, you enter park, bowl, and bad street territory, where gaining speed and not losing it at the first crack matters.
The Conical Full cut has the widest contact surface in the conical family, which provides more support in turns and more wheel to wear down.
